The aging mouse exhibits a severely depressed immune response. The defect(s) can be corrected by transfer of thymus influenced lymphocytes (T) or by a synthetic non-toxic adjuvant polyadenylic-polyuridylic acid complexes (poly A poly U) which has been shown to affect T lymphocytes. The long term objectives are to understand the nature of the defect(s) in aging mice and the mechanism by which poly A poly U reinstates antibody synthesis. Since cell-cell cooperation between the macrophage, T and B cells is required for an effective immune response, the investigators will test the effect of this adjuvant on each of these cells and its capacity to influence the secretion of soluble enhancing and suppressing factors through which these cells communicate. In particular, the secretion of interleukin I and II will be tested in the presence of poly A and poly U and the appropriate cell types. Proliferation of target cells in culture under the influence of these mediators will be measured. In addition, the means by which aging breeder mice respond to immune stimuli and aging virgin mice do not will be explored with experiments testing nutritional hormonal and temporal effects in these two groups.